Data commit

Task/Prime-decomposition/FreeBASIC/prime-decomposition.basic

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+' FB 1.05.0 Win64
+
+Function isPrime(n As Integer) As Boolean
+  If n Mod 2 = 0 Then Return n = 2
+  If n Mod 3 = 0 Then Return n = 3
+  Dim d As Integer = 5
+  While d * d <= n
+    If n Mod d = 0 Then Return False
+    d += 2
+    If n Mod d = 0 Then Return False
+    d += 4
+  Wend
+  Return True
+End Function
+
+Sub getPrimeFactors(factors() As UInteger, n As UInteger)
+  If n < 2 Then Return
+  If isPrime(n) Then
+    Redim factors(0 To 0)
+    factors(0) = n
+    Return
+  End If
+  Dim factor As UInteger = 2
+  Do
+    If n Mod factor = 0 Then
+      Redim Preserve factors(0 To UBound(factors) + 1)
+      factors(UBound(factors)) = factor
+      n \= factor
+      If n = 1 Then Return
+      If isPrime(n) Then factor = n
+    Else
+      factor += 1
+    End If
+  Loop
+End Sub
+
+Dim factors() As UInteger
+Dim primes(1 To 17) As UInteger = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59}
+Dim n As UInteger
+For i As UInteger = 1 To 17
+  Erase factors
+  n = 1 Shl primes(i) - 1
+  getPrimeFactors factors(), n
+  Print "2^";Str(primes(i)); Tab(5); " - 1 = "; Str(n); Tab(30);" => ";
+  For j As UInteger = LBound(factors) To UBound(factors)
+     Print factors(j);
+     If j < UBound(factors) Then Print " x ";
+  Next j
+  Print
+Next i
+Print
+Print "Press any key to quit"
+Sleep